This application claims the priority of German Patent Application, Serial No. 102 36 941.0, filed Aug. 12, 2002, pursuant to 35 U.S.C. 119(a)-(d), the disclosure of which is incorporated herein by reference.
The invention is directed to a laminated stator core for an electric machine, in particular to a laminated stator core for a synchronous harmonic machine.
Stators of so-called harmonic motors have to satisfy specific requirements. Harmonic motors are motors where the number of rotor poles corresponds to an integer multiple, e.g., 2, 3, 4, . . . of the fundamental number of stator poles. The stator teeth of such harmonic motors should have high and wide tooth heads, and the stator slots should have a high copper fill factor.
Laminated stator cores with slots between the tooth heads that are manufactured by inserting the respective stator winding into the slots are known in the art. However, a high copper fill factor cannot be achieved by using this technique.
A laminated stator core of this type is known from DE 198 05 981. It consists of a radially arranged yoke packet with inwardly oriented poles or conical teeth or necked teeth, respectively. When the stator is manufactured, a respective pole coil is wound around each necked tooth, and a tooth head is secured to the necked tooth with the winding. However, such stators can disadvantageously not be used with harmonic motors.
It would therefore be desirable and advantageous to provide an improved laminated stator core for a harmonic motor, which obviates prior art shortcomings, can be more easily manufactured and allows a higher copper slot fill factor.
According to one aspect of the invention, the object is solved by a laminated stator core for an electric machine, in particular for a synchronous harmonic machine, with an essentially cylindrical bore and a plurality of pole teeth extending radially inwardly in the bore. Each of the pole teeth have an inner free end, wherein the inner end of each second pole tooth has, as viewed in the circumferential direction, a fixed tooth head. A pole tooth with a removable head is arranged between each two pool teeth with a fixed tooth head, as viewed in the circumferential direction.
This approach, where only every second tooth is provided with both a winding and a tooth head, advantageously results not only in a high slot fill factor, but also in small air gaps at the joints and small areas with magnetic interference while simultaneously simplifying installation. Moreover, the stator can have a uniform height with a reduced stray flux.
Preferably, the stator core includes pole teeth in the circumferential direction with wider and narrower necks, wherein the tooth head on each wider necked teeth is removable. In this way, the windings can be easily applied on the wider necked teeth, wherein the narrower necked teeth are left without a winding.
It is advantageous for the installation to attach each removable tooth head on the corresponding necked tooth by a snap connection. One element of the snap connection is provided with a groove and the other element is provided with a complementary projection. When the two components are connected, the projection engages with the other groove. The walls of the groove are initially spread apart when the tooth head and necked tooth are joined, if the groove includes a recess and the complementary projection includes at its distal end a corresponding extension. When the tooth head and the necked tooth are finally pushed together, the walls of the groove snap together slightly, i.e., in the direction to the unstressed state. This produces a releasable snap connection.
Preferably, one of the components of the snap connection can include a locking element which in the installed state presses an elastic component of the snap connection into a locked position. In this way, in the walls of the tooth groove can be urged towards each other at the end of the snap-in motion, so that the protuberance at the distal end of the snap connection projection can no longer be easily pulled out of the recess located on the tooth groove.
The removable tooth heads are preferably laminated in the form of strips, which allows cost-effective fabrication of tooth heads that can be easily installed.
As mentioned above, that aforedescribed laminated stator core can be used to manufacture stators with windings arranged around the wide necked teeth. Such stators are particularly suited for harmonic motors.